1. Field of the Invention
The invention relates generally to methods and devices used for determination of analytes in saliva or other body fluid, and in particular, pertains to an integrated device and method to carry out chemical and immunochemical analysis simultaneously and including a sensor strip for determination of ammonia.
2. Description of the Related Art
Helicobacter pylori (formerly called Campylobacter pylori) was first isolated by Warnell and Shall in 1983 (Marshall B. J., Warren J. R., Lancet 1984:1:1311-5). H. pylori is the most widespread bacteria infection with an estimated worldwide prevalence of 50% (Marshall B. J., Epidemiology of H. pylori in Western countries. In: Hunt R. H., Tytgat G. N. J., eds. Helicobacter pylori: Basic Mechanisms to Clinical Cure. Dordrecht: Kluwer Academic Publishers. 1994:75-84; Hazell S. L., H. pylori in developing countries. In: Hunt R. H. Tytgat G. N. J., eds. Helicobacter pylori: Basic Mechanisms to Clinical Cure, Dordrecht: Kluwer Academic Publishers, 1994:85-94). H. pylori is a very important pathogen in several diseases of the stomach and duodenum. H. pylori is associated with type B gastritis, duodenal ulcer, gastric ulcer, and gastric cancer.
A variety of methods has been developed for diagnosis of H. pylori infection and evaluation of eradication of H. pylori following antibacterial treatment.
U.S. Pat. No. 5,498,528 teaches a method for detection of H. pylori strain comprising the steps of contacting a saliva sample suspected of containing H. pylori directly with a urea containing medium selective for growth of H. pylori and having a pH of about 5.5 to 7.5, and incubating the sample for a time sufficient for detection of H. pylori growth in at least 80% of true positive samples. The method is based on hydrolysis of urea contained in the growth medium by urease enzyme produced by H. pylori and detection of a hydrolysis product by release of a radioactive label from urease or by a color change resulting from action on a pH indicator. The time required to obtain a result by the method disclosed is a function of temperature, approximately 2-3 days when incubated at 23-25.degree. C. and 4-6 hours when incubated at 35-37.degree. C.
U.S. Pat. No. 5,479,935 teaches an ambulatory system for recording and analyzing gastroesophageal reflux. The system comprises a digital recorder, an analysis software package and a catheter for measurement of changes in esophageal impedance. Gastroesophageal reflux can be detected with a pH above 4. The invention allows for recording and analysis of reflux on a non-invasive basis, by using pairs of externally worn impedance sensors. Other bio-parameters, such as pH or pressure can be measured simultaneously with impedance measurement.
U.S. Pat. No. 5,477,854 teaches a system and a method for monitoring intragastrointestinal concentrations of ammonium during prolonged periods, as an indicator of the presence and activity of an intragastrointestinal H. pylori infection. The system may be used in the evaluation of treatments for H. pylori infection in the patient.
U.S. Pat. No. 5,439,801 teaches an improved test for the detection of the presence of urease associated with H. pylori in a biopsy specimen. The hydrolysis of urea by urease is detected by a combination of at least two dye indicators showing a color change. Most positive results occur in 2-10 minutes and all occur in no more than four hours.
U.S. Pat. No. 5,438,985 teaches a method and a system for ambulatory recording of the pH and the presence of various materials in compartments of the gastro-intestinal tract. The invention also reports the pH pattern in relation to the prevalence of the materials, and analysis to which degree such materials are in active or inactive states in their normal or foreign compartments. This is useful in situations, for example, when duodenal material is refluxed into the stomach and esophagus. The invention involves a gastrointestinal catheter with a pH sensor and a combined light absorption and fluorescence sensor, a signal recorder and processor, and a written report producer.
U.S. Pat. No. 5,420,016 and U.S. Pat. No. 5,314,804 teach a rapid method for determining the presence of H. pylori in a biological tissue specimen by detecting the presence of urease in the tissue. The system employs a multilayer test device for the detection of ammonia generated from urea at the presence of urease in the specimen.
U.S. Pat. No. 5,420,014 teaches a method of detecting contemporary infection by H. pylori in a mammal. The method is based on the formation of complex between a specific IgG antibody in said mucous secretion and an antigen component from H. pylori. The antigen component is immobilized onto a solid support.
U.S. Pat. No. 5,262,156 teaches an assay for detecting H. pylori. The assay involves an ELISA for urine samples, and includes a kit wherein the antigenic composition is immobilized on a solid support.
U.S. Pat. No. 4,947,861 teaches a non-invasive method for detection of C. pylori. A breath sample is collected from a patient ten minutes after the patient ingests a quantity of urea. The sample is dehydrated by passing through a solid-state body of alkaline hygrosopic material and analyzed for ammonia. The presence of ammonia indicates presence of C. pylori in the stomach.
U.S. Pat. No. 4,882,271 teaches a method for the serological detection of C. pylori. An antigen for the detection of C. pylori infections is purified from C. pylori. The antigen can be used in a variety of assays including radioimmunoassay, ELISA, latex agglutination, complement fixation, and indirect hemagglutination.
The urea breath test based on the extremely high endogenous urea activity of H. pylori is a reliable and non-invasive method with high sensitivity and specificity suitable for diagnosis and evaluation tests; however, the application of the urea breath test is restricted by high cost in isotope-labeled material, time, expensive equipment, and undesirable radioactive exposure to C.sup.14.
Against this background there remains a need for a method of diagnosing C. pylori that is rapid, non-invasive, and able to distinguish infection in an active state from dormant or non-living residues.